Tuesday, September 29, 2009

Ancient Australian Trace Fossils Hint at Martian Equivalents

The hope for primitive life on Mars has received a new boost. Early bacteria that lived 2.75 billion years ago shaped caves to live in, and the traces left behind hint at how life might still be inhabiting Mars. In a recent Discovery Channel article, Michael Reilly describes an early Earth with no oxygen in the atmosphere, or ozone layer to protect anything living on the surface from harmful ultraviolet radiation. This is the earliest evidence of subterranean life on Earth. In the article Birger Rasmussen of Curtin University of Technology in Bentley, Australia describes evidence that these ancient bacteria colonized tiny hollows in lake and river sediments.

The tiny hollows were just a centimeter or so tall and a couple of millimeters across, and formed air-tight sheets, which were inflated by methane gas, generated by decaying organic matter, bubbling through the sediments.

This methane could have been a nutrient for the bacteria, or it could have allowed water and nutrients to flow through the cavity. Over time layer upon layer of material built up and formed the laminate fossils Rasmussen's team discovered.

Living in underground cavities allowed the bacteria to escape the UV radiation that scoured the surface. Here was a tiny, protected environment for life.

The team's finding, published this month in the journal Geology, helps substantiate the hypothesis that bacteria colonies might still be hiding out within caves on Mars. Today the Martian surface is desolate, and far too harsh to support life , but recent discoveries of buried water ice revealed by meteor strikes raise tantalizing promise of hidden niches for a simple and hardy life.

The complete article can be found here:

URL: http://www.msnbc.msn.com/id/30649087/